A starter head typically consists of a starter pinion which is arranged to be displaced axially on a motor shaft until it comes into mesh with a toothed crown carried by and around the flywheel of the engine. A free wheel and a driving sleeve, which are secured together by a securing cap, are associated with the starter pinion. Sealing of the free wheel is obtained by the use of two half rings which are associated with a seal. A starter head of this kind is described for example in the specification of French patent application No. 88 14753 (U.S. Pat. No. 2,639,064).
In the method of making a starter head of this kind, after the driving sleeve has been offered up to the starter pinion (to which the free wheel has already been fitted), the two half rings are positioned on the driving sleeve, the seal is fitted into the securing cap, and the securing cap, carrying the seal, is then offered up on to the sub-assembly consisting of the pinion, the driving sleeve and the half rings. The securing cap is then reformed around the half rings in such a way that the various components mentioned above are thereby secured together. This reforming operation is one of particular delicacy, because it is absolutely essential that the two half rings shall remain at all times perfectly sealed together, so that there is no loss of grease from within the free wheel. Any such escape of grease would lead to damage and eventual failure of the starter as a whole.
In the method just described, it is the seal that acts as the locating means for the two half rings; while the securing cap is being reformed, compression of the seal guarantees total immobilisation of the half rings. However, it is almost impossible to fit the seal into the securing cap, and to maintain it in a precise position, by any automatic (robotic) means. This results in an unacceptable cost of production of the starter, when the starters are to be mass produced as is the case in the motor industry.